Many polymer articles are designed for use in cold weather applications. Such polymer articles include machine parts, housings and covers, sports equipment and the like. For example, high performance snow ski boots are made from polymer compositions that are intended to have good impact resistance properties at colder temperatures so that the boots will not crack or otherwise fail during use.
In the past, various problems have arisen in designing high performance snow ski boots. For instance, problems have arisen in attempting to formulate polymer compositions having excellent impact resistance properties at lower temperatures without compromising other properties of the material. Consequently, further improvements are needed in formulating compositions used for producing cold weather sports equipment, such as ski boots. Increasing the impact resistance properties of the polymer composition especially at lower temperatures will allow designers of ski boots to make the walls of the ski boot thinner, thereby not only reducing the weight of the product but also increasing the performance.
Another problem that has been faced by ski boot manufacturers is the ability to produce polymer compositions whose physical properties remain constant over a wide temperature range. For example, since thermoplastic polymers exhibit temperature-dependent behavior, ski boots have a tendency to vary in stiffness, in feel, and in performance as the temperature of the environment changes. For example, the same ski boot may perform differently at a temperature of 0° C. in comparison to at a temperature at −10° C. These differences are very noticeable to a high level skier. In fact, many snow skiers who compete at high levels are known to bury their ski boots in the snow when air temperatures increase in order to increase stiffness and obtain consistent performance out of the ski boot. Small property changes in the ski boot can have a significant impact on a ski competitor's performance, especially when many contests are decided by a fraction of a second.
In view of the above, a need currently exists for an improved polymer composition for use in cold weather environments. In particular, a need exists for molded articles made from a polymer composition that not only has excellent impact resistance properties but also displays stable modulus properties over a broad temperature range.